Silicone elastomers and silicone gels have been widely used in the cosmetic industry. In many cases such as in the antiperspirant area, gels are produced by adding a gelling agent to the vehicle. In a number of formulations, low viscosity volatile silicone oils (such as cyclomethicones) are used as the vehicle and a gelling agent, typically a solid such as stearyl alcohol and/or hydrogenated castor oil, are added thereto so as to gel the liquid vehicle in the course of formulating the complete product.
In other contexts, polymeric materials that swell in the vehicle, but do not dissolve in it are polymerized and subsequently dispersed in the vehicle. A common problem with such gels is that as dispersions of solid in liquid, they tend to disperse light and therefore yield products that are translucent at best and hazy, cloudy, or even opaque at worst. Such products are also expensive in that they require a substantial amount of the elastomeric material in order to have the desired viscosity. If the concentration is too low (in order to improve clarity), the viscosity is generally unacceptably low for a gel. On the other hand, when the viscosity is in the acceptable range, the clarity of the composition suffers. Typical patents in the field utilizing a dispersion technique include U.S. Pat. No. 6,387,405; U.S. Pat. No. 6,083,900; U.S. Pat. No. 6,027,738; U.S. Pat. No. 5,919,468; and EP 0295886, all of which are incorporated (in their entirety) herein by reference.
Other efforts at improving the viscosity of the silicone gels has focused on the use of silicone resins. In the silicone polymer field, the term resin is generally utilized for silicones having a structure in which a significant number of the silicon atoms are connected to at least three and typically four other silicon atoms via oxygen links. However, when such resins are utilized, they frequently result in cross linked gels that are also unacceptable in that the viscosity and/or clarity are outside of desired limitations. Typical patents relating to silicone resins include U.S. Pat. No. 6,423,322; U.S. Pat. No. 6,143,308; U.S. Pat. No. 5,760,116; U.S. Pat. No. 5,266,321; all of which are incorporated by reference herein in their entirety.
Still other efforts at modification of the elastomeric cross-linked siloxanes have included variations on the addition polymerization reaction of a polyorganohydrosiloxane (a siloxane having Si—H bonds) and an unsaturated polyorganosiloxane. This hydrosilylation reaction is typically carried out in the presence of a catalyst, typically platinum. One variation is to graft alkoxy or alkoxylol groups onto the silicone backbone (U.S. Pat. No. 6,331,604, incorporated herein by reference in its entirety). Another variation has been to use a non-silicone unsaturated molecule to crosslink the polyorganohydrosiloxane or to extend the size of the silicone cross links (U.S. Pat. No. 5,880,210, incorporated herein by reference in its entirety). Yet other variations have been to introduce polyethoxy or polypropoxy or polyethoxy/polypropoxy bridges into the cross-linked polymer (EP 0545002, incorporated herein by reference).
Still further variations on the theme have been to polymerize polyorganohydrosiloxane with unsaturated polyorganosiloxane where the number of reactive groups per molecule in the two reactants is varied or the polymerization reaction is carried out in a different vehicle or a different concentration of vehicle (U.S. Pat. No. 4,970,252; U.S. Pat. No. 4,987,169, both incorporated herein by reference in their entirety).
Notwithstanding all of this activity in the silicone gel area, there have still been difficulties in meeting the needs for a silicone gel having an extremely clear appearance, and a viscosity that is in the appropriate range as well as having an appropriate skin feel, and yet be economical. There have also been difficulties in obtaining the appropriate gel material that can have the above properties and be at a relatively low concentration so as to allow for incorporation of other useful components for various product compositions.